What is the difference between an abscess and a boil?

Difference Between an Abscess and a Boil

A boil (furuncle) is a specific type of skin infection involving a hair follicle, while an abscess is a broader term for any collection of pus within the skin or deeper tissues, which may have various causes beyond hair follicle infection. 1

Key Differences

Boil (Furuncle)

• Definition: Infection of a hair follicle caused primarily by Staphylococcus aureus 1
• Characteristics:
  • Always involves a hair follicle
  • Presents as an inflammatory nodule with an overlying pustule through which hair emerges 1
  • Suppuration extends from the hair follicle through the dermis into subcutaneous tissue
  • Usually smaller and more superficial than general abscesses
  • When multiple adjacent follicles become infected, they form a carbuncle (a coalescent inflammatory mass with pus draining from multiple follicular orifices) 1

Abscess

• Definition: A localized collection of pus within the dermis and deeper skin tissues 1
• Characteristics:
  • Typically presents as painful, tender, fluctuant red nodules with surrounding erythematous swelling 1
  • Can form in any tissue, not just around hair follicles
  • Usually polymicrobial (containing normal skin flora bacteria)
  • S. aureus is present as a single pathogen in only about 25% of cutaneous abscesses 1
  • May be classified as simple or complex based on location and extent 1

Causative Organisms

• Boils: Predominantly Staphylococcus aureus (single pathogen) 1
• Abscesses: Typically polymicrobial, containing bacteria from normal regional skin flora, often combined with organisms from adjacent mucous membranes 1

Treatment Approaches

Boils (Furuncles)

• Small furuncles: Application of moist heat to promote drainage 1
• Larger furuncles: Incision and drainage 1
• Systemic antibiotics usually unnecessary unless extensive surrounding cellulitis or fever occurs 1

Abscesses

• Primary treatment: Incision, thorough evacuation of pus, and probing the cavity to break up loculations 1
• Simple covering of the surgical site with a dry dressing is usually effective 1
• Antibiotics generally not needed for simple abscesses unless:
  • Systemic signs of infection are present
  • Patient is immunocompromised
  • Source control is incomplete
  • Significant surrounding cellulitis exists 1

Special Considerations

Recurrent Infections

• For recurrent boils or abscesses, consider:
  • Searching for local causes (pilonidal cyst, hidradenitis suppurativa, foreign material) 1
  • Staphylococcal decolonization with intranasal mupirocin, chlorhexidine washes, and decontamination of personal items 1
  • Evaluation for neutrophil disorders in adults if recurrent abscesses began in early childhood 1

Complex Abscesses

• Complex abscesses (perianal, perirectal, or at injection sites) may require broader antibiotic coverage and more extensive drainage procedures 1

Common Pitfalls

• Misdiagnosing epidermoid cysts (often incorrectly called "sebaceous cysts") as infected abscesses 1
• Inadequate drainage of abscesses or boils leading to recurrence or extension of infection
• Unnecessary use of antibiotics for simple, adequately drained abscesses or boils 1, 2
• Failure to identify and address predisposing factors for recurrent infections 1

Remember that both conditions respond best to appropriate drainage procedures, with antibiotics playing a secondary role only in specific circumstances.